(57) A crank axle includes an axle body having first and second ends, a first rotary linkage
member (51) disposed at the first end of the axle body for nonrotatably fitting a
first crank arm (1) thereto, and a first centring structure (52) disposed at the first
end of the axle body in close proximity to the first rotary linkage member (51). If
desired, the rotary linkage member may be formed as a plurality of splines, and the
same structure may be formed at the second end. A crank arm for fitting to the crank
axle includes a crank axle mounting section (21) having a centring structure (24)
for centring the crank axle mounting section to an end of a crank axle (5), and a
rotary linkage member (23) for nonrotatably fitting the crank axle mounting section
(21) to the end of the crank axle. A special bolt (54) is used to fix the crank arm
to the crank axle. The bolt (54) includes a head (541), a threaded section (542) having
a diameter greater than or equal to the head, and a flange (55) disposed between the
head and the threaded section. The flange preferably has a diameter greater than the
diameter of the threaded section, and the head defines a multiple-sided tool-engaging
hole (59) which extends axially into the threaded section to maximise the tool engaging
surface. The crank axle mounting section (21) of the crank arm preferably includes
a stop ring or similar structure located so that the flange (55) of the bolt (54)
is disposed between the stop ring and the first end of the axle body. As a result,
the bolt flange presses the crank arm apart from the crank axle when the bolt is loosened.
Special tools may be provided to allow easy installation and removal of the components.
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